Echochrome, is no longer "up in the air" for the North American market. When it comes down to earth, however, it'll strictly be in the form of a digital download. Newsweek's N'Gai Croal confirms that the game will only be available through the PlayStation Network store, thereby ruling out a retail-bound UMD like that released in Japan. The PSP version will come with 56 unique levels, a number roughly in line with the (PSN-only) PlayStation 3 version.
So, what about those 100 levels on the Japanese Echochrome UMD? For now, it looks like they'll only be obtainable if you import the game. Echochrome is out in North America this May.